Propane power

I currently have a gravely pro turn 152 with the Kohler EFI engine. I have explored the option of running propane in the past but it seems the mowers that are ready to go from the factory are expensive or they only offer 60+ inch decks. Bobcat does have the predator-pro in a 52in that's propane but that looks like it.

Does anyone have experience running propane? I've been told that generally $20 or so will cut about 40 (1/2 acre or under) properties and they run very clean compared to a gasoline powered mower.

I would also like to know if anyone has any experience with the propane 400 series of Gravely, seems like a good option but with the 72" deck they are only offering the 25 hp motor and I feel it might be to little for such a big deck.

Propane is definitely a good way to go. I saved a ton of money buying a Predator Pro LP. Its hard to beat $1.99 a gallon for fuel in the summer. Im getting out of the business due to loss of a big contract, and only doing landscaping part time, so the Predator is for sale if anybody is interested.